This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A fundamental question is: How can one segregate and analyze a sound-producing object in a complex acoustic environment? By combining behavior and physiology, carefully framing the behavioral question, and using signal detection theory based analyses we will achieve three aims. Aim 1: To measure and compare macaque and human perceptions of fill-in. Aim 1 will be achieved by measuring macaques'and humans'abilities to detect the continuity of foreground sounds as a function of the duration of gaps inserted into them and the intensity of an interrupting noise. Aim 2: To determine neural correlates of fill-in using analyses that allow for direct comparisons of auditory cortical neurons'responses to the results of Aim 1. Aim 3: To determine the strength of association between neural responses and behavioral performance and decisions in multiple cortical fields. To achieve Aims 2 nd 3, signal detection theory based analyses--similar to analyses referred to in the previous paragraph about the visual system--will be used. Achieving the aims will significantly advance the understanding of neural responses contributions to auditory perceptions and decision-making.